Patent Application
20240375446
The present application claims priority to European Patent Application No. 23172091.3 filed on May 8, 2023, which application is incorporated herein by reference in its entirety.
The invention relates to studded tyres. The invention relates to studded pneumatic tyres. The invention relates to studded pneumatic tyres for cars.
Functions of a tyre on an automotive vehicle include providing sufficient traction for accelerating, driving, and braking; and providing adequate steering control particularly at high speeds. Traction is commonly referred to as grip and steering control as handling. There is a constant need for improving grip and handling of tyres.
Grip is affected also by the ground on which the tyre is commonly used. Winter tyres, which are intended for icy roads, are commonly equipped with studs to improve grip on ice. However, the weather may change so that winter tyres need to be usable also on roads, on which there is water, slush, and/or snow. Naturally, also winter tyres need to be usable on dry road.
Grip on roads having water and/or slush are improved, when the water and/or slush is adequately driven away from a contact area between the road and the tyre tread. Thus, in principle, by using large grooves, water is well driven away. However, too many grooves and/or too large groove may worsen handling on bare roads and/or reduce grip, because stability of the tread blocks are reduced and tread blocks are more subject to deformation. Grip on snow, as well as on ice, may be improved by using softer material, provided by the softness of the rubber material as such and/or by sipes provided on the tread. However, too soft material and/or too many sipes may worsen handling.
It has been found how good handling and grip properties of a studded tyre can be simultaneously achieved. According to a first aspect of the invention, an average land ratio of the studded tyre is within a certain limit as detailed in the claims and in the description. According to a second aspect of the invention, a land ratio of a central area of a tread of the studded tyre is greater than either or both land ratios of the shoulder areas of the tread of the studded tyre. According to a third aspect of the invention, a density of sipes on a central area of a tread of the studded tyre is greater than a density/the densities of sipes on one or both of the shoulder areas of the tread of the studded tyre.
Referring to
Some measures of a tyre 200 are depicted in
In practice, the tyre width W200 is related to the size marking shown on the tyre 200. In general, the size marking is shown on a tyre as w/hRr, wherein w denotes a width, h an aspect ratio and r a radius. According to the ETRTO standards manual, typical size markings refer to Design Width (i.e. the width W200 of the tyre 200) and an overall diameter as shown in the Table 1 below:
It is noted that Table 1 shows only some examples. A tyre may have a different size, in particular another aspect ratio than 55.
The tread blocks 220 of the tyre 200 define a land portion LP of the tread 210. A part of the land portion LP of the tread is shown by black colour in
The tread blocks 220 of the tyre 200 define an envelope surface. The envelope surface consists of the land portion LP of the tread 210 and the regions defined by the openings of the grooves 230. The openings of the grooves 230 may be commonly referred to as a sea portion SP of the envelope surface, as shown in black colour in
Thus, the total envelope area A210 is the sum of the land area A220 and the sea area A230, i.e. A210=A220+A230. Referring to
In this description, an average land ratio refers to the ratio of the total land area A220 to the total envelope area A210. In other words, by land ratio is meant the ratio of the ground contacting surface area of tread blocks to the imaginary ground contacting area of the tread, the imaginary ground contacting area of the tread including spaces (i.e. groove openings) between adjacent blocks and the blocks themselves. In other words, by land ratio is meant the ratio of the ground contacting surface area of tread blocks to a ground contacting area of an imaginary tread, the imaginary tread having been formed from the tread by filling the grooves with tread material.
In the art, one sometimes uses the term sea area ratio to mean the ratio of the sea area to the imaginary ground contacting area of the tread. In line with these definitions the sum of the land ratio and the sea area ratio equals one.
In the art, the term “land-to-sea ratio” may, occasionally, be used interchangeably with the land ratio as defined above. However, the term land-to-sea ratio or land/sea ratio may relate to a ratio of the land area (ground contacting area) to the sea area (the non-contacting area only) of the tread. To avoid possible confusion, the term land area is used throughout this description and in the meaning defined above.
According to the first aspect of the invention the average land ratio of the tyre 200 is 55% to 78%. Preferably, the average land ratio of the tyre 200 is 61% to 75%, and more preferably 65% to 72%. The most preferable value is about 67%. This improves drainage of water and/or slush from underneath the studded tyre, when used on wet surface.
In general, increasing the land ratio improves the grip on dry road (including ice), but at the same time decreases the grip on wet and snowy roads (having water and/or slush). The range disclosed above has been found to provide an optimal compromise in studded tyres, which are used during winter.
As shown in Table 2 below, when the average land ratio increases, the grip on ice also improves.
For the data shown in Table 2, three tyres (A, B, and C) were tested. The tyres A and C are identical except that A has been provided with studs, while the tyre C lacks studs. As expected, the tyre A performs much better on ice than the tyre C. For the tyre B, the average land ratio was increased, compared to the tyre A. In addition, the land ratio was optimized so that in the tyre B (unlike in the tyre A), the central land ratio was greater than the shoulder land ratio. In the Table 2 the acceleration, braking, circle handling, and ice handling results are given in relative terms. A higher number indicates better performance. As shown by the results, the grip and handling on ice improves when the average land ratio is increased. As indicated therein, the tyre B is superior compared to the tyre A.
According to the second aspect of the invention, a land ratio of the tread is greater in a central area than in a shoulder area.
The tread blocks 220 define the land portion LP of the tread and the envelope surface as detailed above.
The land portion LP of the tread has a central land area. The central land area is the area of the part of the land portion LP of the tread 210 that belongs to the central region CR. The land portion LP of the tread has a first shoulder land area. The first shoulder land area is the area of the part of the land portion LP of the tread 210 that belongs to the first shoulder region SR1. The land portion LP of the tread has a second shoulder land area. The second shoulder land area is the area of the part of the land portion LP of the tread 210 that belongs to the second shoulder region SR2. Reference is made to
The envelope surface (i.e. the combination of the land portion LP and the sea portion SP) has a central envelope area. The central envelope area is the area of the part of the envelope surface that belongs to the central region CR. The envelope surface has a first shoulder envelope area. The a first shoulder envelope area is the area of the part of the envelope surface that belongs to the first shoulder region SR1. The envelope surface has a second shoulder envelope area. The second shoulder envelope area is the area of the part of the envelope surface that belongs to the second shoulder region SR2. Reference is made to
The tyre has a central land ratio of the tyre 200. The central land ratio is defined as a ratio of the central land area to the central envelope area. According to the second aspect of the invention the central land ratio is 1 to 30 percentage points greater than either or both of a first shoulder land ratio and a second shoulder land ratio. Preferably, the central land ratio is 1.5 to 25 percentage points greater than either or both of a first shoulder land ratio and a second shoulder land ratio. More preferably, the first shoulder land ratio and the second shoulder land ratio are equal.
Herein the first shoulder land ratio is the ratio of the first shoulder land area to the first shoulder envelope area and the second shoulder land ratio is the ratio of the second shoulder land area to the second shoulder envelope area.
Thus, according to the second aspect of the invention proportionally more grooves are arranged in the shoulder region(s) SR1, SR2 than in the central region CR. This improves drainage of water and/or slush from underneath the tyre, when used on wet and/or snowy surface. This shows e.g. as widening of the grooves towards the sides of the tread, as clearly seen from
Naturally, the second aspect of the invention works particularly well when also the average land ratio is within the limits defined by the first aspect of the invention.
Preferably both the shoulder regions SR1, SR2 have substantially equal land ratios. Thus, preferably, a ratio of the first shoulder land ratio to the second shoulder land ratio is 0.8 to 1.2 such as 0.9 to 1.1.
What has been said above concerning the land ratios of the tyre have been found to function well at least in tyre of the classes M1 or N1 (see above). This is also related to a width of the tread 210 of the tyre, since the water/slush is intended to be drained away from the contact area of the tread. Thus, preferably, the tyre 200 has a width W200 that is 150 mm to 350 mm. The width W200 of the tyre 200 is shown in
The first width W210 (i.e. that of the tread) may be equal to the reference tread width as defined in the ETRTO standards manual 2023 (see Design Guide, Page PC.7). In accordance with the definitions therein, the reference tread width C is calculatable as
C=(1.075−0.005ar)s1.001
Herein s is the Section Width (defined above), i.e. the width W200 of the tyre, and ar is the nominal aspect ratio, which is readable from the size marking w/hRr (see above), the “h” indicating the aspect ratio. Thus, the first width W210 of the tread 210 may equal the value C as calculatable with the equation given above, wherein s equals W200.
Such a tyre is preferably manufactured by vulcanizing a green tyre to form the tyre 200 and forming stud holes 250 to the tread 210 of the tyre 200 during the vulcanizing the green tyre.
To improve the grip, the tread 210 is sufficiently soft. The softness can be affected by tread material as such and by using sipes. Thus, in an embodiment, the tread 210 comprises rubber material having a Shore hardness in the range 48 to 59 Sh(A) as measured with durometer type A, at the temperature 23° C. In an embodiment, the tread 210, in particular the part of the tyre that is configured to contact a road in use, is formed of rubber material having a Shore hardness in the range 48 to 59 Sh(A) as measured with durometer type A, at the temperature 23° C. In an embodiment, at least some of the tread blocks 220 are provided with sipes 240. Preferably all the tread blocks 220 have been provided by at least one sipe 240. Sipes 240 are shown in
A tyre having sipes is preferably manufactured by vulcanizing a green tyre to form the tyre 200 and forming the sipes 240 to the tread 210 of the tyre 200 during the vulcanizing the green tyre by using lamella blades.
In accordance with the third aspect of the invention, a density of sipes on a central region of a tread of the studded tyre is greater than a density of sipes on one or both of the shoulder regions of the tread of the studded tyre. Herein the term density of sipes refers to the total length of the sipes 240, which open to the land portion LP of the tread, as divided by the area of the envelope surface. Thus, a unit of the density of sipes is a unit of a length divided by a unit of an area, e.g. cm/dm2 or dm/dm2. Moreover, the length of the sipe 240 is defined at the level of the opening of the sipe 240. Thus, the length of the sipes 240 measured on the tread surface.
More specifically, according to the third aspect of the invention, at least some of the tread blocks 220 of the central region CR of the tread 210 are provided with sipes 240 such that the tyre 200 has a first density of sipes 240. Herein the first density of sipes refers to the density of the sipes in the central region CR. Thus, the first density of sipes 240 is defined as a total length of the sipes 240 arranged in the central region CR, the length measured on the tread surface, divided by the area of the central region CR. The area of the central region refers to the area of the part of the envelope surface that belongs to the central region, i.e. including the sea portion of the tread that belongs to the central region. More precisely, the total length of the sipes 240 arranged in the central region CR refers to the sum of the lengths of the sipes 240 (or parts thereof) that are arranged in the central region CR, the length of each sipe being measured on tread surface of the tyre. The tyre is preferably an unworn tyre.
At least some of the tread blocks 220 of the first shoulder region SR1 are provided with sipes 240 such that the tyre 200 has a second density of sipes 240. Herein the second density of sipes refers to the density of the sipes in the first shoulder region SR1. Thus, the second density of sipes 240 is defined as a total length of the sipes 240 arranged in the first shoulder region SR1, the length measured on the tread surface, divided by the area of the first shoulder region SR1. The area of the first shoulder region SR1 is the area of the part of the envelope surface that belongs to the first shoulder region. More precisely, the total length of the sipes 240 arranged in the first shoulder region SR1 refers to the sum of the lengths of the sipes 240 (or parts thereof) that are arranged in the first shoulder region SR1, the length of each sipe being measured on tread surface of the tyre. The tyre is preferably an unworn tyre.
At least some of the tread blocks 220 of the second shoulder region SR2 are provided with sipes 240 such that the tyre 200 has a third density of sipes 240. Herein the third density of sipes refers to the density of the sipes in the second shoulder region SR2. Thus, the third density of sipes 240 is defined as a total length of the sipes 240 arranged in the second shoulder region SR2, the length measured on the tread surface, divided by the area of the second shoulder region SR2. The area of the second shoulder region SR2 is the area of the part of the envelope surface that belongs to the second shoulder region. More precisely, the total length of the sipes 240 arranged in the second shoulder region SR2 refers to the sum of the lengths of the sipes 240 (or parts thereof) that are arranged in the second shoulder region SR2, the length of each sipe being measured on tread surface of the tyre. The tyre is preferably an unworn tyre.
In accordance with the third aspect of the invention the first density of sipes 240 is at least 15% greater than either or both of the second density of sipes 240 and the third density of sipes 240. Preferably, the first density of sipes 240 is at least 25% greater than either or both of the second density of sipes 240 and the third density of sipes 240. Preferably, the first density of sipes 240 is at least 15% or at least 25% greater than both of the second density of sipes 240 and the third density of sipes 240. More preferably, the first density of sipes 240 is at least 30% greater or at least 35% than either or both of the second density of sipes 240 and the third density of sipes 240. In a preferable embodiment, the second density of sipes is equal to the third density of sipes. In a preferable embodiment, the tyre is not antisymmetric.
The difference in the densities of sipes has the effect that the tread in the central region is less rigid than at the shoulder region(s) SR1, SR2. This improves grip on snowy surfaces.
Also preferably, the second and third densities of sipes are substantially equal. More specifically, preferably a ratio of the second density of sipes to the third density of sipes is 0.8 to 1.2, more preferably 0.9 to 1.1.
As an example, a tyre comprises, in the central region CR sipes 240 so that first density of sipes, i.e. the ratio of a total length of the sipes in the central region CR to an area of such a part of the envelope surface that belongs to the central region CR, is 72 cm/dm2. As conventional, dm2 refers to square decimetre, i.e. (dm)2. The total length of the sipes in the central region CR is measured as defined above. Moreover, the tyre comprises such first and second shoulder regions SR1 and SR2 that are equally wide. The tyre comprises in the first shoulder region SR1 sipes so that the second density of sipes, i.e. a ratio of the total length of the sipes in the first shoulder region SR1 to an area of such a part of the envelope surface that belongs to the first shoulder region SR1, is 51 cm/dm2. The tyre is not antisymmetric, whereby the tyre comprises in the second shoulder region SR2 sipes so that the third density of sipes, i.e. a ratio of the total length of the sipes in the second shoulder region SR2 to an area of such a part of the envelope surface that belongs to the second shoulder region SR2, is also 51 cm/dm2. In this example, the tread consists of the central region CR, the first shoulder region SR1 and the second shoulder region SR2. Moreover, a width WCR of the central region CR was 37% of the width W200 of the tyre 200.
As calculatable from the values given above, in this specific example, the first density of sipes is 41% greater than the second density of sipes. Since the second density of sipes equals the third density of sipes, the first density of sipes is 41% greater than the third density of sipes. An area of the envelope surface depends on the size of the tyre. However, the area may be e.g. of the order of 20 dm2 to 80 dm2 giving and idea of the total length of the sipes in the whole tread.
In addition, preferably, no sipe 240 is provided close to a stud hole 250, in which a stud has been installed. Referring to
However, because the sipes 240 provide for additional grip through effective softening the tread and providing further edges of tread material, preferably at least one or some of the sipes are arranged reasonably close to the stud. Thus, in a preferable embodiment, a stud has been installed in a stud hole 250 such that a part of a sipe 240 is arranged closer than 12 mm to a centre of the stud hole 250. More preferably, a stud has been installed in a stud hole 250 such that a part of a sipe 240 is arranged closer than 10 mm (or closer than 9 mm) Thus, in an embodiment, the tyre comprises such a stud and such a sipe that a distance from a part of the sipe to a centre of the stud hole 250 is, e.g., 6 to 12 mm, 6 to 10 mm, 6 to 9 mm, 8 to 12 mm, 8 to 10 mm, or 8 mm to 9 mm (one significant digit, and in line with the text above, excluding the upper end-points of these ranges but including the lower end-points of these ranges). It is noted that the reference DSS only stands for such a measure that no part of any of the sipes 240 is arranged closer than the distance DSS to a centre of the stud hole 250, to a centre of the stud hole 250.
Most preferably, a stud has been installed in a stud hole 250, and no part of any of the sipes 240 is arranged closer than 8 mm to a centre of the stud hole 250 and a part of at least one of the sipes is arranged closer than 10 mm to a centre of the stud hole 250. Preferably this applies to multiple studs so that parts of different sipes may be close to different stud holes. Thus, preferably, at least parts of multiple studs (100, 100a, 100b) are arranged in multiple stud holes 250 provided in multiple tread blocks 220, and no part of any of the sipes 240 is arranged closer than 6 mm to a centre of any one of the stud holes 250 (preferably no part is arranged closer than 8 mm to a centre of any one of the stud holes 250); and the tyre comprises multiple such sipes that a part of each one of the multiple sipes 240 is arranged closer than 12 mm (preferably closer than 10 mm) to a centre a stud hole 250 to which a stud has been arranged.
The third aspect of the invention may be used in combination with the first aspect of the invention (only). The third aspect of the invention may be used in combination with the second aspect of the invention (only). The third aspect of the invention may be used in combination with both the first and the second aspects of the invention. The first aspect of the invention may be used in combination with the second aspect of the invention, optionally without the third aspect of the invention.
In an embodiment, a width WSR1 of the first shoulder region equals a width WSR2 of the second shoulder region. The widths are shown in
In general a sipe 240 is a much narrower opening in the tread than a groove 230.
In contrast, a groove 230 is wider. In an embodiment, a width W230 of at least one of the grooves 230, as measured on the level of the tread 210 limiting the groove 230, is more than 4.0 mm. The width W230 is shown in
The grooves may taper radially inward (i.e. in the −SR direction). Thus, in an embodiment, a width W230 of at least one of the grooves 230 decreases in an inward radial direction −SR of the tyre. Reference is made to
A depth of a sipe 240 is less than a depth of a groove 230. More specifically, in an embodiment, a depth D240 of all the sipes 240 is at most equal to a depth D230 of one of the grooves 230. A bottom of a sipe needs not be even. In such a case the depth of the sipe 240 refers to a depth of the deepest point of the sipe. In an embodiment, a depth of all the sipes 240 is at least 2.0 mm.
In terms of depth, preferably an average of the depths D240 of the sipes 240 arranged in the first shoulder region SR1 of the tread 210 is not greater than an average of the depths D240 of the sipes 240 arranged in the central region CR. Likewise, preferably, an average of the depths D240 of the sipes 240 arranged in the second shoulder region SR2 of the tread 210 is not greater than an average of the depths D240 of the sipes 240 arranged in the central region CR. This has the effect that the sipes 240 provided in the shoulder region(s) SR1, SR2 do not soften the tread material too much by being too deep. This is related to handling of the tyre in the same way as the different densities of sipes detailed in connection with the third aspect of the invention.
In a preferable embodiment, at least some of the grooves 230 are inclined such that they define a V-shape or a half of a V-shape, the V-shape or the half thereof defining a direction of rotation R of the tyre 200 when used driving forward, the direction of rotation R being reverse to the direction to which the V-shape or the half thereof opens. As an example, the grooves of
As detailed above, the tyre 200 comprises studs 100. An example of a stud 100 is shown in
Referring to
The base flange 140 has a first cross-section on a plane that has a normal in the longitudinal direction Sz of the stud, the first cross-section having a first area A140. Moreover, the base flange 140 has a profile shape extending at least a certain distance in the direction of the normal of the first cross-section. As shown in
The pin 110 has a second cross-section on a plane that has a normal in the longitudinal direction Sz of the stud 100, the second cross-section having a second area A110.
In the embodiment of
The waist 132 has a third cross-section on a plane that has a normal in the longitudinal direction Sz of the stud, the third cross-section having a third area A132.
Moreover, the second flange 134 has a fourth cross-section on a plane that has a normal in the longitudinal direction of the stud, the fourth cross-section having a fourth area A134.
The fourth area (that of the cross-section of the second flange 134) is greater than the third area A132 (that of the cross-section of the waist 132). The fourth area (that of the cross-section of the second flange 134) is greater than the second area A110 (that of the cross-section of the pin 110).
The first area A140 (that of the cross-section of the base flange 140) is greater than a cross-section of the second part A130. A stud may comprise a second part 130 that does not comprise a waist and a second flange. In such a case the first area A140 (that of the cross-section of the base flange) is greater than the sole cross-section of the second part A130. However, the first area A140 may be greater than both of the third area A132 of the cross-section of the waist 132 and the fourth area A134 of the cross-section of the second flange 134.
To provide a good grip of the stud 100, the base flange 140 should be sufficiently large so that the dynamic impact, which the stud imposes to the road upon contact, is sufficient. Moreover, the pin 100 should be sufficiently small in order to intrude well to ice. For these reasons, preferably, a ratio A140/A110 of the first area A140 to the second area A110 is 6.5 to 21. Preferably, the ratio A140/A110 of the first area A140 to the second area A110 is 7.5 to 19, and more preferably 9 to 17.
Also, to provide a good grip, the pin 110 should protrude from second part 130 (e.g. from the second flange 134) sufficiently. A first height H110, which is the first height that the pin 110 protrudes from the second flange 134 (or in the more general case, from the second part 130) is depicted in
The pin 110 and the second part 130 define the first height H110, which is the length the pin 110 protrudes from the interfacial point 112 in the longitudinal direction Sz to the extremal point 114 of the pin 110 in the longitudinal direction Sz of the stud.
It has been found that for good grip, the first height H110 should be selected such that a ratio A140/H110 of the first area A140 to the first height H110 is 20 to 50 mm2/mm. Preferably, the ratio A140/H110 of the first area A140 to the first height H110 is preferably 25 to 48 mm2/mm, and more preferably 28 to 45 mm2/mm. For fixing the stud firmly to stud holes, in an embodiment, the first area A140 is 20 mm2 to 80 mm2, preferably 30 mm2 to 70 mm2.
In an embodiment a mass of the stud 100 is 0.4 g to 3 g, preferably 0.5 g to 1.5 g, most preferably 0.65 g to 1.1 g. In an embodiment a mass of the pin 110 is 0.1 g to 0.8 g, preferably 0.15 g to 0.35 g. A length L110 of the pin 110 may exceed the first height H110. These measures are shown in
To keep the stud 100 in the stud hole 250 firmly, the first cross-section of the base flange 140 should be sufficiently large. In addition or alternatively, the stud 100 should be sufficiently long. Thus, in an embodiment, a height H100 of the stud, as measured in the longitudinal direction Sz of the stud 100 is greater than 9.5 mm. The height H100 is preferably 10.0 to 11.0 mm. Reference is made to
Moreover, in an embodiment, a length dn140 of a shortest straight line that connects an edge of the first cross-section, an opposite other edge of the first cross-section, and a central point O of the first cross-section is 4.5 mm to 9.5 mm, preferably 4.5 mm to 8.5 mm, and most preferably 5.0 to 7.5 mm. A shortest line that connects an edge of the first cross-section, an opposite other edge of the first cross-section, and a central point O of the first cross-section and the length dn140 thereof is shown in
These measures each one separately and some or all in combination ensure that the stud 100 remains well in the stud hole 250 in use, and therefore ensure good grip of the tyre 200.
The second cross-section of the pin 110 may have various shapes. An example of the second cross-section is shown in
Starting with forms having multiple axes of symmetry,
Preferable shapes of the tip 110 include such shapes that the second cross-section has one, two, or three (but not more than three) axes of symmetry. Thus, in an embodiment, the second cross-section has at least one and at most three axes such axes of symmetry S that belong to the plane of the second cross-section. Having one, two or three axes S of symmetry improves the possibilities of optimizing the grip by orienting the stud (e.g. one of the axes of symmetry) relative to the direction of rotation R. Thus, this number of axes S of symmetry is beneficial in combination with the tyre being directional (see above for definition).
The tyre comprises multiple studs. Preferably, the tyre comprises multiple such studs that have been disclosed above.
All the studs 100 of the tyre 200 may be identical. Thus, in an embodiment, the tyre 200 comprises studs 100 of only a first stud type.
However, the tyre 200 may comprises at least two different types of studs. As shown in
In an embodiment, at least two thirds of the studs 100 that are arranged in the central region CR are of the second stud type (they are studs 100b), and at least two third of the studs arranged in the first and second shoulder regions SR1, SR2 are of the first stud type (they are studs 100a).
In an embodiment, the studs 100a of the first stud type comprise identical first pins. A cross-section of a first pin, the plane of the cross-section having a normal to the longitudinal direction Sz of the stud, has a first shape. Moreover, the studs 100b of the second stud type comprise identical second pins. A cross-section of a second pin, the plane of the cross-section having a normal to the longitudinal direction Sz of the stud, has a second shape. The second shape is different from the first shape. For example, the pin 110 of the stud 100a of the first type, as shown in
By using at least two different types of studs, the grip of the tyre can be optimized. This is particularly true, when studs of the second type are used in the central region CR, and studs of the first type are used in the shoulder regions SR1, SR2.
The grip of the tyre can be improved by using sufficiently many studs. The grip of the tyre can be improved by using sufficiently many studs on both sides of the circumferential central line CL.
Concerning the former, in an embodiment, the tread 210 has the first width W210 and the first circumference C210, as defined above. Moreover, the tread 210 is provided with a total number N100 of studs 100. In an embodiment, a ratio (N100/(W210×C210)) of the total number N100 of the studs to the product W210×C210 of the first width W210 and the first circumference C210 is more than 5.6 pieces per square-decimetre (pcs/dm2). The first circumference C210 may be measured along the circumferential central line CL, e.g. along a circumferential central line of the envelope surface of the tread 210.
Concerning the latter, in an embodiment, the circumferential central line CL of the tread 210 defines a first half of the tread 210 and a second half of the tread 210. In the embodiment, the first half comprises a first number N1 of studs 100, 100a, 100b and the second half comprises a second number N2 of studs 100, 100a, 100b such that a ratio (N1/N2) of the first number to the second number is 90% to 110%.
Referring to
Referring to
Preferably, the circumferential central line CL of the tread 210 defines the first half of the tread 210 and the second half of the tread 210, and the studs are arranged such that at least three different circumferential rows (r11, r12, r13, r14, r15, r16, r17, r18, r19) of the at least six different circumferential rows (r11, r12, r13, r14, r15, r16, r17, r18, r19, r21, r22, r23, r24, r25, r26, r27, r28, r29) are arranged on the first half, and at least three different circumferential rows (r21, r22, r23, r24, r25, r26, r27, r28, r29) of the at least six different circumferential rows (r11, r12, r13, r14, r15, r16, r17, r18, r19, r21, r22, r23, r24, r25, r26, r27, r28, r29) are arranged on the second half.
Having such many rows rij effective spreads the studs to the tread 210 reasonably evenly, thereby improving the grip.
Preferably the tyre 200 is configured such that a road wear of the tyre is minimized. Road wear of a tyre is defined as the road wear in the test specified in the standard SFS7503:2022:en. The standard SFS7503:2022:en specifies the test procedure in detail. On the general level, a vehicle equipped with the tyres to be tested is driven over test specimens with specified speed to a specific number of times. The average wear of test specimens is expressed in units of mass (i.e. in grams). The less the tyres wear the road, the less is the result (grams) of the test. In an embodiment, the multiple studs 100, 100b, 100a and of the tyre 200 and the tread 210 of the tyre are configured such that a road wear of the tyre 200 as measured according to the standard SFS7503:2022:en is less than 1.0 g, preferably less than 0.87 g, and more preferably less than 0.79 g.
The road wear is correlated with a dynamic impact of the studs 100. The low value of road wear may be achieved e.g. by having a sufficiently low dynamic impact of the studs to the road, particularly when driving at the speed indicated in the road wear standard. Features affecting the dynamic impact of the studs to the road include:
Both the first area A140 and the rubber material supporting the base flange 140 have effect on how sturdy the stud is supported to the rubber material of the tyre.
In addition to the tread 210 of the tyre 200, the structure of the tyre 200 provides for sufficient rigidness of the tyre 200 and thereby also affect the handling properties of the tyre 200. The tread 210 is provided as an outermost layer of a carcass of the studded tyre 200. A quarter of a cross-section of a tyre 200 is shown in
As detailed above, the tyre comprises the tread blocks 220 that define the grooves 230 and the tread 210, which is an outermost layer of the carcass. Preferably, the carcass of the studded tyre 200 comprises one or more layers of reinforcing textile or textiles and one of more reinforcing metal layers.
In general, a tyre 200 has side surfaces on opposite sides of the tread 210. The side surfaces connect the bead area of the tyre to the tread 210. The side surfaces may have various markings indicating the tyre size, tyre speed class, tyre purpose (winter/summer), tyre manufacturer and/or tyre name. The bead area of a tyre has a cable. The function of the cable and the bead area is to fit the tyre 200 to the rim.
The tyre 200, in particular the carcass thereof, comprises a first ply 288. The ply 288 may comprise fibrous material, e.g. Kevlar, polyamide, carbon fibres, or glass fibres.
The carcass further comprises a first metal belt 287. Preferably, the carcass further comprises a textile belt 284, such as a textile belt 284 comprising fibrous polyamide (e.g. Nylon, aramid, or Cordura). Preferably, the carcass further comprises the textile belt 284 and a second metal belt 286. The metal belt(s) 287, 286 is/are resilient metal belts, such as steel belts comprising wires.
The tread blocks 220 are comprised by a cap layer 23 of the tyre 200. The cap layer 23 may further comprise material connecting the tread blocks 220. Thus, the cap layer 23 forms at least part of a running surface of the tyre. Thus, the cap layer 23 forms at least part of an outer surface of the tread. Under the tread blocks 220 of the tread 210, i.e. under the cap layer 23, the tyre preferably comprises an underlayer 21 made of suitable rubber material. A purpose of the underlayer 21 is to support the studs 100 so that they properly contact the ground in use. Thus, in an embodiment, the studs 100 of the tyre 200 are arranged at least partly on the underlayer 21. Thus, the underlayer 21 affects the dynamic impact the studs have on the road.
Referring to
The underlayer 21 can be a circumferential layer. The underlayer 21 can be disposed radially outside an outermost belt of the tyre, such as a textile belt 284 or a metal belt 286, 287. If the tyre comprises a textile belt 284, the underlayer 21 can be disposed radially outside the textile belt 284. Technical effect of the textile belt is to restrict expansion from centrifugal forces during driving at high speed as well as improve many properties of the tyre having the underlayer, including improved handling, grip and aquaplaning for the tyre comprising the underlayer. If the outermost belt of the tyre is a metal belt 286, 287, the underlayer 21 can be disposed radially outside the metal belt 286, 287. The underlayer 21 has an inner surface 25 and an outer surface. The outer surface of the underlayer faces the tread 20. The inner surface 25 of the underlayer substantially faces the center of the tyre 200.
By the combined effect of the underlayer 21, the ply 288, and the metal belt or belts (286, 287), the dynamic impact of the studs can be particularly well controlled at different ambient temperatures.
The underlayer 21 is preferably arranged at least partly below the studs 10. Thus, the studs 100 can be placed at least partly above the underlayer 21. Preferably, the underlayer 21 is arranged to be under each of studs of the winter tyre so that the base flange of the stud can be pressed against and retract into the underlayer 21.
The stud 100, preferably the base flange 140 of the stud, can be in direct contact with the underlayer 21. Thus, preferably, there is no other material layer between the stud and the underlayer.
Preferably, at least part of a base flange 140 of a stud is surrounded by the underlayer 21, and at least part of the second flange 134 of the stud is surrounded by the cap layer 23. Technical effect is to support the stud and decrease road wear.
More preferably, also an intermediate layer 22 is used, and at least part of a waist 132 of the stud 100 is surrounded by the intermediate layer 22. Technical effect is to improve stud retention as well as support the stud. More details of the intermediate layer 22 will follow.
The underlayer has an average thickness 21t. The average thickness 21t of the underlayer can be at least 0.5 mm, such as between 0.5 mm and 8 mm, more preferably at least 1.0 mm, and most preferably at least 1.5 mm. Furthermore, the average thickness 21t of the underlayer can be equal to or less than 7 mm, more preferably equal to or less than 6.5 mm, and most preferably equal to or less than 6 mm. The average thickness can be, for example, between 1 mm and 6 mm. Technical effect is that the ice grip properties of the stud can be substantially improved at cold weather, and moreover, the road wear at warm weather can be substantially reduced. Moreover, the underlayer of the presented thickness can be compressible to reduce road wear, to reduce tyre noise, to improve the driving performance of the tyre as well as to keep the pin of the stud protruded from the tread to provide the tyre with good grip on an icy driving surface.
In an embodiment, the underlayer has a hardness (ShA) between 45 ShA and 65 ShA, determined at an ambient temperature of 22° C. according to standard ASTM D2240. Herein (in below) the unit ShA refers to the Shore A hardness, i.e. hardness as determined in the “A” scale of the standard. Technical effect is that the underlayer 21 is able to reduce road wear at 22° C. Preferably, the underlayer has a hardness (ShA) between 45 ShA and 60 ShA, more preferably between 45 ShA and 55 ShA, determined at an ambient temperature of 22° C. according to standard ASTM D2240. These values may apply also at 23° C.
Preferably, the tyre has such an underlayer 21 that a hardness of the underlayer varies with the temperature. Technical effect is to decrease the road wear of the studded tyre but still provide desired winter grip properties in spite of the reduced road wear. Hardening/softening of the material may occur at a temperature that can be characterized by a measuring part of a complex modulus of the material as discussed below. In particular, a position of a tan delta maximum of the material may characterize a temperature at which hardening/softening takes places.
In an embodiment, a position of a tan delta maximum of the underlayer 21 is configured to be between −10° C. and +15° C., determined according to ISO 4664-1:2011 in compression. Technical effect is that in warm conditions, the underlayer can substantially soften, whereby the underlayer can allow the stud body to retract into the tread of the tyre, whereby it can reduce the stud's dynamic impact and thereby reduce the wear of the road.
The position of the tan delta maximum refers to the temperature at which tan delta reaches its maximum value. As background, the values of tan delta, as function of temperature, is referred to as a tan delta curve. The values for tan delta curve of this specification are determined as follows: Dynamic Mechanical Thermal Analysis (“DMTA”) tests provide information about the small-strain mechanical response of the samples as a function of temperature. Sample specimens can be tested using a commercially available DMTA equipment in compression mode according to the standard ISO 4664-1:2011. The specimen is cooled to −60° C. and then heated to 70° C. at a rate of 2° C./min (i.e. 2 K/min) while subjected to an oscillatory deformation and a static strain, the oscillatory deformation having a frequency. Examples of specific values are detailed below. The output of the DMTA test is the storage modulus (E′) and the loss modulus (E″), both as function of temperature. The storage modulus indicates the elastic response or the ability of the material to store energy, and the loss modulus indicates the viscous response or the ability of the material to dissipate energy. The ratio of E″/E′, called tan delta, gives a measure of the damping ability of the material. As discussed, tan delta depends on temperature. Peaks in tan delta are associated with relaxation modes for the material, such as glass transition. The term “position of tan delta maximum” refers to a temperature in which the maximum value of a tan delta curve is obtained. Thus, “position of tan delta maximum” can be determined, for example, as a position of maximum tan delta value of the tan 8 curve.
The tan delta values can be determined from rubber compounds of a tyre as well as from rubber compounds to be used for a tyre, before forming the tyre. The sample has dimensions of diameter 4.5 mm× height 5.0 mm, when determined from a tyre. Further, the sample has dimensions of diameter 10.0 mm×height 10.0 mm, when determined from a rubber compound.
As for the values of oscillatory deformation and a static strain, for example, the following value can be used in the DMTA measurements:
The position of a tan delta maximum of the underlayer is thus the temperature at which the tan delta of the underlayer reaches it maximum. Correspondingly, the position of a tan delta maximum of the intermediate layer is the temperature at which the tan delta of the intermediate layer reaches it maximum.
From the DMTA measurements, also the dynamic stiffness (E*) of the material (underlayer of intermediate layer, whichever is tested) can be determined as detailed in the standard ISO 4664-1:2011 in a compression test. The values can be determined from rubber compounds using the procedure disclosed above for tan delta.
The dynamic stiffness of the underlayer, determined at a temperature of 20° C., can be configured to be less than 25 MPa, preferably from 5 to 20 MPa.
The dynamic stiffness (E*, MPa) of the underlayer can be
The change in the dynamic stiffness of the underlayer upon a decrease in the temperature can have a greater impact on the grip of the tyre in winter than the change in the hardness of the material upon a decrease in the temperature. For the above-mentioned dynamic stiffness values, the adjustment of the stud's dynamic impact of the tyre at different temperatures can be more controllable, and the grip properties of the winter tyre can be better optimized for different temperatures. Thanks to the above-mentioned dynamic stiffness, for example the braking distance on an icy road can be substantially reduced.
These properties of the underlayer 21 can be achieved by a proper composition of the material of the underlayer 21.
Preferably, the underlayer 21 contains
A combined amount of carbon black and/or silica (examples of reinforcing fillers) is preferably from 35 to 80 phr, more preferably from 40 to 70 phr.
Technical effect of materials comprising the rubbers comprising at least 30 phr solution polymerized styrene-butadiene rubber together with the reinforcing filler(s) and the resin(s), and preferably also 10 to 70 phr NR, BR, and/or IR, is to provide the desired tan delta curve for the rubber compound.
The underlayer 21 can further contain additives, such as one or more of oils, antidegradants, ZnO, stearic acid, vulcanization chemicals and sulphur.
As discussed, the reinforcing fillers can comprise carbon black, and/or silica.
If the reinforcing fillers comprise silica, silane can be added for improving reinforcing efficiency of the silica. Preferably, a content of the silane is equal to or less than 15% by weight, such as between 5 wt. % and 15 wt. %, determined from total weight of the silica in the underlayer. Technical effect it to provide improved dispersion. Furthermore, silane can form bonds between silica and rubber during the vulcanization.
As discussed, the underlayer 21 preferably contains styrene butadiene rubber which is solution-polymerized styrene butadiene rubber SSBR. The underlayer 21 can comprise at least 30 phr of SSBR. Thus, the content of SSBR in the underlayer 21 can be at least 30 phr, preferably at least 35 phr, more preferably at least 40 phr, and most preferably at least 45 phr. Further, the content of SSBR in the underlayer 21 can be equal to or less than 100 phr, preferably equal to or less than 90 phr, more preferably equal to or less than 80 phr, and still more preferably equal to or less than 70 phr. By using said contents of the solution-polymerized styrene butadiene rubber SSBR, the stiffness can be efficiently adjusted as desired.
Microstructure of SSBR has an effect on properties of the SSBR. When preparing the underlayer, the vinyl content of the solution-polymerized styrene butadiene rubber, is preferably between 33% and 65% by weight, more preferably between 38% and 61% by weight, wherein the vinyl contents are expressed in mol % relative to the butadiene. Furthermore, the styrene content of the styrene butadiene rubber is preferably between 25% and 45% by weight, most preferably between 27% and 40% by weight, wherein the styrene content is expressed in mass % relative to the whole polymer. The contents can be determined by 1H-NMR method in accordance with ISO 21561-1:2015.
This embodiment can provide particularly suitable properties for the underlayer so that stiffening of the underlayer can take place in a controlled manner. Thus, stiffening can take place at a moment determined more precisely in advance.
Preferably, the underlayer contains either NR and SSBR, or BR and SSBR. In these combinations, the technical effect of NR and BR is to improve the elasticity of the underlayer even at cold temperatures. Further, the technical effect of SSBR is to improve stiffness of the mixture.
Thus, advantageously, the underlayer contains
Technical effect of said combination of NR and SSBR is that the position of tan delta maximum can be efficiently adjusted as desired, and hardness of the underlayer can increase at a desired temperature, particularly when used together with the reinforcing fillers and resins according to this specification. Furthermore, thanks to this combination, elasticity of the underlayer can be maintained at cold temperatures, further improving properties of the underlayer.
It is to be noted that the natural rubber NR can be replaced with a synthetic isoprene rubber and still maintain the technical effects of the natural rubber. The synthetic isoprene rubber IR is very much like natural rubber but made synthetically. Thus, from 0 to 100 wt. % of the natural rubber NR can be replaced with the synthetic isoprene rubber IR.
In an embodiment, the underlayer advantageously contains
Technical effect is that properties of the studded tyre having the underlayer can be particularly improved and position of the tan delta maximum of the underlayer can be easily adjusted by using said amounts of polybutadiene rubber and the solution polymerized styrene-butadiene rubber, particularly when used together with the reinforcing fillers and resins according to this specification.
The underlayer 21 can contain reinforcing fillers. A total amount of the reinforcing fillers is preferably more than 30 phr, more preferably at least 33 phr, still more preferably at least 35 phr, and most preferably at least 40 phr, determined from the underlayer 21. Furthermore, the underlayer 21 can comprise equal to or less than 80 phr of reinforcing fillers, preferably equal to or less than 70 phr of reinforcing fillers, still more preferably equal to or less than 60 phr of reinforcing fillers, and most preferably equal to or less than 55 phr of reinforcing fillers. Technical effect of the reinforcing fillers is that the hardness of the underlayer is easier to optimize to a desired level.
The reinforcing fillers are preferably selected from silica and carbon black. The reinforcement may comprise both silica and carbon black. If the reinforcing fillers comprises silica, also silane is preferably added to the mixture. Technical effect of the reinforcing fillers is to improve the strength of the underlayer. Furthermore, the reinforcing fillers can be used to influence the ShA hardness of the underlayer so that the hardness of the underlayer can be more easily optimized to a desired level.
In a non-limiting embodiment, the carbon black is selected from N375 and N234. These carbon blacks are known by a person skilled in the art.
In an embodiment, silica can be selected from: anhydrous silica prepared by dry process and silica prepared by wet process. Among them, hydrous silica prepared by wet process is preferable because it contains a lot of silanol groups.
In a non-limiting embodiment, the silica is selected from high BET and low BET.
Silane coupling agent can be used for silica to be appropriately dispersed during kneading. Preferably, a content of the silane is between 5 wt. % and 15 wt. %, determined from total weight of the silica in the underlayer. Technical effect it to provide improved dispersion. Furthermore, silane can form bonds between silica and rubber during the vulcanization.
The silane coupling agents can be of any type known to those skilled in the art. For example, at least one of bifunctional organosilane and polyorganosiloxane can be used. “Bifunctional” means a compound having a first functional group capable of interacting with silica, e.g., alkoxy, cycloalkoxy or phenoxy group as a leaving group on the silicon atom, and a second functional group capable of interacting with the double bond of elastomer, e.g., —SCN, —SH, —NH2 or —Sx- where x=2 to 8. The organosilanes can be chosen from the group consisting of polysulphide organosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulphide, abbreviated as TESPT or bis disulphide-(triethoxysilylpropyl), abbreviated as TESPD, polyorganosiloxanes, mercaptosilanes or blocked mercaptosilanes.
The underlayer 21 can contain oil(s). The amount of oils, if used, can be at least 5 phr, more preferably at least 8 phr, and most preferably at least 10 phr. Further, the amount of oils can be equal to or less than 25 phr, preferably equal to or less than 22 phr, and most preferably equal to or less than 20 phr. Technical effect is to increase processability and adjust hardness of the compound.
The oil(s) is/are preferably selected from the group of:
Preferably, said oil contains or consists of at least primarily TDAE oil and/or SRAE oil. Technical effect of oils is to act as process aids and softeners in the manufacturing process.
As discussed, the underlayer 21 can contain one or more resins. A total content of resins is preferably at least 5 phr determined from the underlayer. Technical effect is that the resins can adjust dynamic behavior of the underlayer by shifting and/or broadening the tan delta peak of the rubber compound. Thus, thanks to the resins, position of the tan delta maximum can be adjusted in a cost-efficient and controlled manner to a predetermined temperature range.
A total amount of resins can be at least 5 phr, preferably at least 10 phr, more preferably at least 15 phr, and most preferably at least 17 phr, determined from the underlayer. Further, the total amount of resins can be equal to or less than 40 phr, preferably equal to or less than 35 phr, more preferably equal to or less than 30 phr and most preferably equal to or less than 28 phr, determined from the underlayer. Thus, the total amount of resins can be, for example, 5-40 phr, preferably 10-35 phr, and more preferably 15-30 phr, determined from the underlayer. By applying resin, position of tan delta maximum of the underlayer can be raised by a predetermined level so that the hardening of the underlayer can be implemented within a predetermined temperature range. Another technical effect is that by using the preferably ranges, resins affect the rubber compound by shifting and/or broadening the tan delta peak of the rubber compound as desired.
The resin(s) used for the underlayer can have a glass transition temperature higher than 20° C., more preferably higher than 30° C., and most preferably higher than 35° C. Further, the resin(s) used for the underlayer can have a glass transition temperature of less than 110° C., preferably less than 85° C., most preferably less than 70° C. For example, the resin(s) can have a glass transition temperature from 20 to 100° C., preferably from 35 to 60° C. As discussed, Tg for resins can be determined as a peak midpoint by a differential scanning calorimeter (DSC) at a temperature rate of increase of 10° C. per minute, according to ASTM D6604 or equivalent.
Preferably, the one or more resins of the underlayer are selected from the following group:
Technical effect is to efficiently adjust the position of tan delta maximum to a desired temperature, i.e., to shift a position of tan delta maximum to a desirable range.
Most preferably, the one or more resins of the underlayer are selected from rosin-based resins, terpene-based resins, and pure monomer C9 resins (PMR), i.e., aromatic resins based on aromatic feedstocks that have been highly purified prior to polymerization, including copolymers of styrene and α-methylstyrene. Technical effect is to shift tan delta peak position to a desirable temperature range more efficiently.
The underlayer can comprise an aromatic resin. Thus, the resin(s) can contain aromatic groups. In an embodiment, the resins contain more than 4% aromatic groups, more preferably more than 6% aromatic groups. However, the aromatic content is preferably less than 60%, more preferably equal to or less than 54%.
Advantageously, for adjusting the position of the tan delta peak of the underlayer to a desired temperature range in a controlled and precise manner, the underlayer comprises:
The contents of the materials are preferably in the range defined in this specification.
The underlayer 21 can comprise, primarily comprise, or consist of a material whose tan delta maximum is at a temperature of at least −20° C., for example at least −15° C., preferably at least −12° C., more preferably at least −10° C., or at least −8° C., and most preferably at least −5° C. Furthermore, tan delta maximum of said material can be at a temperature equal to or less than 20° C., for example not higher than 15° C., preferably not higher than 12° C., more preferably not higher than 10° C., or not higher than 8° C., and most preferably not higher than 5° C. Thus, the hardening of the underlayer can be suitable in view of road wear and winter grip. Technical effect of the preferable ranges is that the hardening of the underlayer can take, more accurately, place at a point optimal in view of road wear and winter grip hence, the stud's dynamic impact of the tyre can be controlled easier at different temperatures.
An unvulcanized material of the underlayer can be vulcanized so that sulphur is used as the vulcanizing agent.
As indicate above, the underlayer 21 may be reasonably soft at a high temperature. However, it has been found that a too soft underlayer 21 may not result in optimal handling properties of the tyre. The inventors have found that the handling properties can be, in such a case, improved by using an intermediate layer 22 providing for sufficient rigidness, even if the underlayer 21 is soft. This applies in particular, when the underlayer 21 is made of adaptive material, i.e. material that softens at high temperatures as discussed above. Thus, in an embodiment, the tyre 200 comprises comprises the intermediate layer 22. Moreover, in such an embodiment, the underlayer 21 is arranged, at least partially, under the intermediate layer 22. The intermediate layer 22 can be a circumferential layer.
Even if not shown, a part of the intermediate layer 22 may form a part of the cap layer 23. Thus, in an embodiment, the intermediate layer 22, or at least part of the intermediate layer 22, is be placed between the cap layer 23 and the underlayer 21.
An average thickness 22t of the intermediate layer can be at least 0.4 mm preferably at least 0.5 mm. As for an upper limit, the thickness of the intermediate layer may be at most 7 mm. A preferable range for the thickness is at least 0.6 mm and less than 6.5 mm, more preferably at least 0.7 mm and equal to or less than 6 mm, and most preferably in a range between 0.8 mm and 5 mm. Technical effect is that the intermediate layer can, together with the underlayer, provide the stud with particularly suitable winter grip properties. Thus, the ice grip properties of the tyre can be substantially improved. In addition, properties of the vehicle tyre can be designed as desired more efficiently than in other solutions.
A thickness of the intermediate layer 22, determined at a location wherein the intermediate layer is surrounding a stud, can be at least 0.4 mm and equal to or less than 7 mm, preferably at least 0.5 mm, more preferably at least 0.6 mm and less than 6.5 mm, still more preferably at least 0.7 mm and equal to or less than 6 mm, and most preferably in a range between 0.8 mm and 5 mm. Technical effect is that the intermediate layer can support the stud. Further technical effect is that the intermediate layer can provide particularly suitable handling properties.
The intermediate layer 22 is made of a second rubber compound. In an embodiment, the intermediate layer has a hardness (ShA) between 66 ShA and 80 ShA, determined at an ambient temperature of 22° C. according to standard ASTM D2240. Technical effect is that the intermediate layer is able to improve stability of tyres having the underlayer 21. Preferably, intermediate layer has a hardness (ShA) between 70 ShA and 78 ShA, determined at an ambient temperature of 22° C. according to standard ASTM D2240. These values may apply also at the temperature 23° C.
A position of tan delta maximum of the intermediate layer 22 is, in an embodiment, configured to be between −40° C. and −70° C. (more preferably between −40° C. and −60° C.), determined according to ISO 4664-1:2011 in compression. Further, preferably, at the same time, a position of a tan delta maximum of the underlayer 21 can be configured to be between −10° C. and +15° C. (preferably between −5° C. and +15° C.), determined according to ISO 4664-1:2011 in compression. Thus, when the underlayer substantially softens in warm conditions, the intermediate layer can substantially maintain its stiffness and therefore support the stud and the whole tyre.
The dynamic stiffness of the intermediate layer, determined at a temperature of 20° C., can be configured to be at least 25 MPa, preferably at least 27 MPa, and more preferably from 30 to 100 MPa. Technical effect is to decrease road wear while the intermediate layer supports the whole tyre and the studs of the tyre at the warmer temperature. At the same time, the dynamic stiffness of the underlayer, determined at a temperature of 20° C., can be configured to be less than 25 MPa, preferably from 5 to 20 MPa.
The composition of the intermediate layer 22 affects these properties.
The intermediate layer can comprise or be made of materials selected from a group comprising or consisting of:
In an embodiment, silica may be selected from: anhydrous silica prepared by dry process and silica prepared by wet process. Among them, hydrous silica prepared by wet process is preferable because it contains a lot of silanol groups. Silane coupling agent can be used for silica to be appropriately dispersed during kneading.
If the fillers comprise silica, silane can be added for improving reinforcing efficiency of the silica. Preferably, the content of the silane is equal or less than 15% (such as from 5% to 15%) by weight relative to the amount of silica. Technical effect is to improve dispersion and during the vulcanization silane forms bond between silica and rubber.
The silane coupling agents can be of any type known to those skilled in the art. For example, at least one of bifunctional organosilane and polyorganosiloxane can be used. “Bifunctional” means a compound having a first functional group capable of interacting with silica, e.g., alkoxy, cycloalkoxy or phenoxy group as a leaving group on the silicon atom, and a second functional group capable of interacting with the double bond of elastomer, e.g., —SCN, —SH, —NH2 or —Sx- where x=2 to 8. The organosilanes can be chosen from the group consisting of polysulphide organosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulphide, abbreviated as TESPT or bis disulphide-(triethoxysilylpropyl), abbreviated as TESPD, polyorganosiloxanes, mercaptosilanes or blocked mercaptosilanes.
Most preferably, the intermediate layer comprises
As discussed, in an embodiment, the intermediate layer is made of an electrically conductive rubber material.
Preferably, the intermediate layer 22 comprises a rubber reinforcing carbon black. Technical effect is to increase stiffness of the intermediate layer while improving electrical conductivity through the tread. The intermediate layer can comprise a rubber reinforcing carbon black content of at least 40 phr, preferably at least 50 phr. Thus, the rubber composition(s) of the intermediate layer 22 can be relatively electrically conductive. Thus, the relatively electrically conductive rubber composition of the intermediate layer can e.g., form a part of the electrically conductive path. Thus, a very small electrical resistance can be obtained through the cap layer.
The intermediate layer 22 can comprise one or more oils. The oil(s) can comprise, for example,
Preferably, the oil(s) are selected from TDAE and SRAE. The oils can act in the manufacturing process as process aids and softeners.
A total amount of the oils in the intermediate layer 22 can be from 0 to 30 phr.
The resin(s) of the intermediate layer can be selected from the following group:
A total amount of the resins in the intermediate layer 22 can be from 0 phr to 30 phr, preferably 2 to 20 phr. Technical effect of resins is fine tuning stiffness properties of the intermediate layer.
Thanks to the underlayer and the intermediate layer, properties of the tyre can be easier to control so that the underlayer can yield to a particularly suitable extent when the ambient temperature rises, which can further reduce wear of the road surface. Further, by the combined technical effect of the intermediate layer and the underlayer, wear of the road surface under non-frozen conditions can be reduced while the underlayer together with the intermediate layer substantially improves winter grip of the tyre on an icy road.
As for the relation of the hardnesses of the underlayer 21 and the intermediate layer 22, in an embodiment, hardness (ShA) of the intermediate layer is configured to be greater than hardness of the underlayer at 22° C. Said difference between the underlayer and the intermediate layer is preferably at least 10%, more preferably from 10% to 60%, and most preferably from 11% to 40% so that underlayer is at least 10% softer than the intermediate layer, determined at 22° C. Technical effect is that the underlayer yields to a suitable extent at said ambient temperature, which reduces wear of the road surface, while the harder intermediate layer supports the tyre.
In an embodiment, the first rubber compound has a first hardness (ShA) and the second rubber compound has a second hardness (ShA), and a hardness (ShA) difference between the first rubber compound and the second rubber compound is at least 15% determined at −25° C. so that the second rubber compound is at least 15% softer than the first rubber compound, determined according to standard ASTM D2240 with an exception that the hardness is determined at a temperature of −25° C. and the rubber compounds are tempered according to Table 3 of the specification. Technical effect is that the underlayer made of the first rubber compound substantially improves ice grip of the tyre on an icy road.
The hardness (ShA) difference between the underlayer and the intermediate layer at cold temperatures is preferably at least 5%, more preferably from 10% to 60%, still more preferably from 12% to 50%, and most preferably from 15% to 30% so that the underlayer is harder than the intermediate layer, determined at −25° C. Technical effect is that the underlayer and the intermediate layer substantially improves ice grip of the tyre on an icy road.
Accordingly, when measuring the Shore hardness at a temperature which is not disclosed in the standard ASTM D2240; the Shore hardness is measured by first tempering the material to be measured at the reference temperature by keeping the material to be measured at the reference temperature for a time given in Table 3 before the measurements.
A softer underlayer material can substantially increase the retraction of the stud into the tyre at warmer temperatures and thereby reduce road wear and noise. The greater the difference in hardness of the material at different temperatures, the greater the effect of the underlayer on the grip of the tyre in cold weather and on road wear in warm weather. Thus, the effects of the underlayer can be particularly advantageous for both cold and warm conditions.
The dynamic stiffness of the underlayer, determined at a temperature of 0° C., can be configured to be at least two times the dynamic stiffness of the underlayer at a temperature of 20° C. Further, the dynamic stiffness of the intermediate layer, determined at a temperature of 0° C., can be configured to be from 1 to 1.5 times, preferably from 1.1 to 1.4 times, the dynamic stiffness of the intermediate layer at a temperature of 20° C. Technical effect is that the winter grip properties of the winter tyre can be substantially improved while the intermediate layer supports the whole tyre and the studs of the tyre at warmer temperatures.
The dynamic stiffness of the underlayer can be at least 100% higher, preferably at least 150% higher, than the dynamic stiffness of the intermediate layer at a temperature of 0° C. Technical effect is that the ice grip properties of the winter tyre can be substantially improved at 0° C. The dynamic stiffness of the underlayer may further be equal to or less than 1000% higher, such as equal to or less than 900% higher, preferably equal to or less than 580% higher than the dynamic stiffness of the intermediate layer at a temperature of 0° C.
Furthermore, the dynamic stiffness of the intermediate layer can be higher than the dynamic stiffness of the underlayer at a temperature of at least 5° C., such as at a temperature of at least 7° C. In a particularly advantageous embodiments, the dynamic stiffness of the intermediate layer is higher than the dynamic stiffness of the underlayer at temperatures from 10° C. to 20° C. Technical effect is to reduce road wear while improving handling properties of the tyre. Further technical effect is that the intermediate layer effectively supports the stud.
The dynamic stiffness of the underlayer at −25° C. can be at least 20 times the dynamic stiffness of the underlayer at +20° C. Thus, the grip properties of the winter tyre can be substantially improved, and, for example, the braking distance needed by the winter tyre under certain conditions can be substantially reduced.
It was noted during experimental tests that properties of tyres were particularly improved when the position of tan delta maximum of the underlayer was in a range between 0° C. and 10° C., and the position of tan delta maximum of the intermediate layer was less than −30° C. Thus, preferably, the tan delta peak position of the underlayer is in a range between 0° C. and 10° C., and the tan delta peak position of the intermediate layer is equal to or less than −30° C.
In a preferred example, for optimizing the grip properties of the tyre in winter,
During the experimental tests, it was noted that properties of tyres were particularly improved when a cross point of stiffness curves of the underlayer and the intermediate layer (shown in
Thus, advantageously, a cross point of stiffness curves of the underlayer and the intermediate layer is in a range between +5° C. and 20° C., more preferably in a range between +7° C. and 13° C.
In an advantageous embodiment, the dynamic stiffness of the underlayer is higher than the dynamic stiffness of the intermediate layer at temperatures of less than 5° C., but the dynamic stiffness of the intermediate layer is higher than the dynamic stiffness of the underlayer at temperatures from 15° C. to 20° C. Technical effect is to substantially reduce road wear while improving handling properties of the tyre.
As for the materials of the underlayer 21 and the intermediate layer 22, several studded tyres comprising the underlayer and the intermediate layer according to this specification were manufactured. The amounts of raw materials were as disclosed in the specification.
Table 4 discloses, as an example, raw materials of the underlayer and the intermediate layer for one of the manufactured tyres.
The rubber mixtures were obtained by means of a stepwise mixing process. A 2 L-internal mixer (Krupp Elastomertechnik GK 1,5 laboratory mixer) was used to add the compounds.
In the first step, the polymers were added and mixed for 40 seconds. In the second step, part of the carbon black and chemicals were added and mixed for 60 seconds. In the third step, the rest of the carbon black and oil were added and mixed for 90 seconds or temperature in mixing chamber received 150 degrees.
The final step with curing chemicals was performed at 95° C. for 50 seconds.
DMTA samples were vulcanized at 150° C. by using a pressure of 150 bar. The optimum vulcanization time of t90 (at 150° C.) was determined with a moving die rheometer according to ISO 4664-1:2011. A vulcanization time of t90 plus 5 min was used for the samples.
Position of tan delta max, DMTA at 20° C. and at −20° C., and hardness (ShA) at 20° C. were determined from the obtained underlayer and intermediate compounds.
DMTA measurements results of Table 5 were done by using tension mode according to standard ISO 4664-1:2011, by using a temperature range from −60° C. to 70° C., 10 Hz, static strain 3%, and dynamic strain±0.2%.
As can be seen from Table 5, the underlayer as well as the intermediate layer had the desired properties for being able to reduce road wear while improving stability of tyres.
101. A tyre (200) comprising
102. A tyre (200) comprising
103. The tyre of example 102, wherein
104. The tyre of any of the examples 101 to 103, wherein
105. A tyre (200), comprising
106. The tyre (200) of example 105, wherein
107. The tyre of the example 102 or 103, wherein
108. The tyre of any of the examples 104 to 107, wherein
109. The tyre of any of the example 108, wherein
110. The tyre (200) of any of the examples 101 to 109, wherein
111. The tyre (200) of any of the examples 101 to 110, wherein
112. The tyre (200) of any of the examples 101 to 111, wherein
113. The tyre (200) of any of the examples 101 to 112, wherein
114. The tyre (200) of any of the examples 101 to 113, wherein
115. The tyre (200) of any of the examples 104 to 114, wherein
116. The tyre (200) of any of the examples 104 to 115, wherein
117. The tyre (200) of any of the examples 104 to 115, wherein
118. The tyre (200) of any of the examples 104 to 117, wherein
119. The tyre (200) of any of the examples 104 to 118, wherein
120. The tyre (200) of any of the examples 104 to 119, wherein
121. The tyre (200) of any of the examples 104 to 120, wherein
122. The tyre (200) of any of the examples 104 to 121, wherein
123. The tyre (200) of any of the examples 101 to 122, wherein the tyre (200) has been manufactured by
124. The tyre (200) of any of the examples 101 to 123, wherein
125. The tyre (200) of any of the examples 101 to 124, wherein
126. The tyre (200) of any of the examples 101 to 125, wherein
127. The tyre (200) of any of the examples 101 to 126, wherein
128. The tyre (200) of the any of the examples 101 to 127, wherein
129. The tyre of any of the examples 101 to 129, wherein
130. The tyre of any of the examples 101 to 129, wherein
131. The tyre of any of the examples 101 to 130, wherein
132. The tyre of any of the example 130, wherein
133. The tyre (200) of the example 101 or 132, wherein
134. The tyre (200) of the example 101 or 132, wherein
135. The tyre (200) of the example 134, wherein
136. The tyre (200) of the example 135, wherein
137. The tyre (200) of any of the examples 134 to 136, wherein
138. The tyre (200) of any of the examples 101 to 137, wherein
139. The tyre (200) of any of the examples 101 to 138, wherein
140. The tyre (200) of any of the examples 101 to 139, wherein
141. The tyre (200) of the example 140, wherein
142. The tyre (200) of any of the examples 101 to 141, wherein
143. The tyre (200) of any of the examples 102 to 142, wherein
144. The tyre (200) of any of the examples 102 to 143, wherein
145. The tyre of any of the examples 101 to 144, comprising
146. The tyre of the example 145 comprising
147. The tyre of the example 145 or 146, wherein
148. The tyre of any of the examples 145 to 147, wherein
149. The tyre of the example 148, wherein
150. The tyre of any of the examples 145 to 149, wherein
151. The tyre of any of the examples 145 to 150, wherein
152. The tyre of any of the examples 145 to 151, wherein
153. The tyre of any of the examples 145 to 152, wherein the underlayer (21) comprises
154. The tyre of any of the examples 145 to 153, wherein the underlayer (21) comprises a/the solution-polymerized styrene butadiene rubber (SSBR), wherein the solution-polymerized styrene butadiene rubber has, when preparing the underlayer,
155. The tyre of any of the examples 145 to 154, wherein the underlayer contains
156. The tyre of any of the examples 153 to 155, wherein the underlayer comprises one or more reinforcing fillers selected from
157. The tyre of any of the examples 145 to 156, wherein
158. The tyre of any the examples 145 to 157 comprising
159. The tyre of the example 158, wherein
160. The tyre of the example 158 or 159, wherein
161. The tyre of any of the examples 158 to 160, wherein
162. The tyre of any of the examples 158 to 161, wherein
163. The tyre of any of the examples 158 to 162, wherein
164. The tyre of any of the examples 158 to 163, wherein
165. The tyre of any of the examples 158 to 164, wherein the first rubber compound has a/the first hardness (ShA) and the second rubber compound has a/the second hardness (ShA), and a hardness (ShA) difference between the first rubber compound and the second rubber compound is at least 10% determined at −25° C. so that the second rubber compound is at least 10% softer than the first rubber compound, determined according to standard ASTM D2240 with an exception that the temperature is −25° C. and the rubber compounds are tempered according to Table 3 of the specification.
201. A stud (100) for improving grip of a tyre (200), the stud (100) comprising
202. The stud of the example 201,
203. The stud of the example 201 or 202, wherein
204. The stud of the example 203, wherein
205. The stud of any of the examples 201 to 204, wherein
206. The stud of any of the examples 201 to 205, wherein
207. The stud of any of the examples 201 to 206, wherein
208. The stud (100) of any of the examples 201 to 207, wherein
209. The stud (100) of any of the examples 201 to 208, wherein
210. The stud (100) of any of the examples 201 to 209, wherein
211. The stud (100) of any of the examples 201 to 210, wherein
212. The stud (100) of any of the examples 201 to 211, wherein
213. The stud (100) of any of the examples 201 to 212, wherein
214. The stud (100) of any of the examples 201 to 213, wherein
215. The stud (100) of any of the examples 201 to 214, wherein
216. The stud (100) of any of the examples 98 to 110, wherein
| Number | Date | Country | Kind |
|---|---|---|---|
| 23172091.3 | May 2023 | EP | regional |
